Phosphorylation of STEF/Tiam2 by protein kinase A is critical for Rac1 activation and neurite outgrowth in dibutyryl cAMP–treated PC12D cells

• DOI: 10.1091/mbc.e10-09-0783
• Publication Date: 2011-04-02T04:34:27Z
• Authors: Akihiro Goto; Mikio Hoshino; Michiyuki Matsuda; Takeshi Nakamura
• Keywords: Neurite; CDC42; Growth cone; Second messenger system; Small GTPase; Cyclin-dependent kinase 5

The second messenger cAMP plays a pivotal role in neurite/axon growth and guidance, but its downstream pathways leading to the regulation of Rho GTPases, centrally implicated neuronal morphogenesis, remain elusive. We examined spatiotemporal changes Rac1 Cdc42 activity phosphatidylinositol 3,4,5-triphosphate (PIP(3)) concentration dibutyryl (dbcAMP)-treated PC12D cells using Förster resonance energy transfer-based biosensors. During 30-min incubation with dbcAMP, gradually increased throughout remained at maximal level. There was no change PIP(3) concentration. After 5-h were activated protruding tips neurites without accumulation. dbcAMP-induced activation principally mediated by protein kinase A (PKA) Sif- Tiam1-like exchange factor (STEF)/Tiam2. STEF depletion drastically reduced neurite outgrowth. PKA phosphorylates three residues (Thr-749, Ser-782, Ser-1562); Thr-749 phosphorylation critical for extension. outgrowth, plasma membrane became localized tips; this localization may contribute local same tips. Considering PKA-STEF-Rac1 pathway play crucial cytoskeletal during outgrowth which depend on signals.